In Europe, work has been and is being carried out to develop and standardize third-generation mobile radio systems. By way of example, great significance is attached to the “Universal Mobile Telecommunications System” (UMTS), which was developed as part of the 3rd Generation Partnership Project (3GPP).
The UMTS concept makes provision for a user of the UMTS mobile radio system to be provided with a handy terminal for many areas of use.
Like a large number of known communication systems, UMTS is also based on a “layer model” which comprises a plurality of hierarchically organized layers.
The tasks which arise for a communication link are distributed over these layers. The entities on a layer provide services for the entities on the layer above it.
This layer model and a UMTS standard are described in the specifications published by the 3GPP, inter alia in the following: (1) 3GPP TS 25.301: Radio Interface Protocol Architecture; (2) 3GPP TS 25.331: Radio Resource Control (RCC) protocol specification; (3) 3GPP TS 23.107: QoS Concept and Architecture; (4) 3GPP TS 25.321: Medium Access Control (MAC) protocol specification; (5) 3GPP TS 25.133: Requirements for Support of Radio Resource Management; and (6) 3GPP TS 23.060: General Packet Radio Service (GPRS), Service description, Stage 2.
The names used below are based on the names which are also used in the specifications published by the 3GPP.
On the basis of UMTS, the main function of the RRC (Radio Resource Control) layer is managing the communication link between the UMTS radio network, which is called the UMTS terrestrial radio access network (UTRAN), and the user terminal.
A communication link comprises a signaling link and a data link.
The signaling link is used when signaling data (control data) are transmitted between the user terminal and the UTRAN, for example when setting up and terminating the communication between the user terminal and the UTRAN.
The data link is used for transmitting the user data, for example for transmitting audio data.
On the basis of UMTS, four states are defined for the communication link or for the corresponding user terminal, said states also being called RRC states. These states are called CELL_DCH, CELL_FACH, CELL_PCH and URA_PCH.
In a further RRC state, the Idle Mode, there is no signaling link and no data link between the user terminal and the (UMTS) radio network.
The significance of these states is explained more precisely further below.
Clearly, these states correspond to the stages of activity on the communication link between the user terminal and the radio network.
In the RRC state CELL_DCH, there is a dedicated radio link between the user terminal and the UTRAN.
In this state, the user terminal has a respective associated dedicated physical channel for the uplink, i.e. when transmitting data from the user terminal to a mobile radio base station, and for the downlink, i.e. when transmitting data from a mobile radio base station to the user terminal, in order to transmit signaling data and user data.
The properties of the physical channels on the dedicated radio link, preferably a mobile radio link, are specified by the values of various parameters. Examples of these (channel) parameters are explained further below.
When setting up a connection, i.e. when setting up a dedicated radio link, and when configuring the corresponding physical channels, it is necessary for suitable values to be determined for the channel parameters, for example in respect of the desired connection quality and in respect of the available radio resources.
In addition, the parameter values, which are typically determined on the part of the radio network, need to be signaled to the user terminal.
Determining and signaling the parameter values typically requires a considerable time involvement, which results in delays in connection setup.
On the basis of UMTS, “SRNS relocations” are also provided.
During an SRNS relocation, the radio network control unit which is currently associated with a user terminal, i.e. the user terminal's SRNC (Serving Radio Network Controller), changes to a new RNC, which is also called the Target RNC.
Following the SRNS relocation, the Target RNC undertakes the role and hence the tasks of the SRNC in respect of the particular mobile radio user terminal.
SRNS relocations are advantageous on account of the mobility of the user terminals during operation of a UMTS communication system.
During an SRNS relocation, the SRNC sends the Target RNC a multiplicity of parameters, inter alia an RRC information container using an information element called “SRNS Relocation Info”.
This information container is used to signal important information about the user terminal to the Target RNC, this information being required by the Target RNC in order to accept the SRNC's functions following the relocation.
This includes information regarding the parameters configured for the user terminal for the purpose of encryption and for integrity protection and also the radio bearers and transport channels.
On the basis of UMTS, “soft handovers” are also provided. In the text below, handover is understood to mean the process in which a user terminal is “passed on”, while there is a radio link to a mobile radio network, from the coverage area of one radio cell to the coverage area of a new radio cell, that is to say that the radio cell to which the user terminal has, the radio link changes.
A soft handover is a special handover, in the course of which a user terminal has a respective dedicated radio link with a plurality of radio cells simultaneously.
In the case of the soft handover procedure based on the prior art, the decision to effect a handover is made solely by the mobile radio network control unit (RNC), and a soft handover can be performed only if signals from the radio cells in question can be received by the user terminal with sufficient signal quality and if the dedicated radio resources to be allocated which are required for the radio links are available.
For this reason, a significant time involvement is required, particularly when setting up a dedicated radio link in the soft handover.
EP 1 274 203 A1 discloses a method for stipulating a user terminal identifier, which is used when a dedicated logical channel is used to transmit received data using a common transport channel.
GB 2 370 453 A discloses a communication apparatus, with a communication link being used to transmit data subdivided by means of a control apparatus at the first node from a first node to a second node on the basis of a communication protocol. This communication apparatus is particularly suitable for avoiding delays in the use of a packet-based network together with a radio network.
Document US 2003/0007490 A1 discloses a method and an apparatus for packet-based data transmission during an SRNS relocation. For the loss-free SRNS relocation, a method for checking a consecutive packet data convergence protocol (PDCP) number is provided.
WO 01/91420 A2 discloses a method for changing the Internet protocol (IP) address associated with a mobile user terminal during an SRNS relocation.
Document US 2003/0002464 A1 discloses a method for operating a communication terminal in a plurality of modes of activity, where the change from a “traffic” mode to a “suspended” mode can involve status information being stored using a traffic channel which is cleared down upon the change, so that it becomes possible to set up a traffic channel again at an accelerated rate.
U.S. Pat. No. 6,016,428 discloses a method in which parameters associated with activities relating to a first channel are stored while a mobile communication terminal uses a second channel.
U.S. Patent No. 2002/085719 A1 discloses a method for performing a handover from a start access point to a destination access point in a WLAN.
In respect of the further standardization of UMTS within the 3GPP committees, currently appropriate improvements for rapid and efficient data transmission via the dedicated transport channel (dedicated channel, DCH) are being examined, particularly for the uplink.